e3/9 vs e28 Power Steering Pump

[Bav3.5]

Has anyone switched to an e28 535 power steering pump from the original e3? Is there a significant pressure difference that would increase the steering effort?

Also, I have to tighten the mounting bolts really tight, otherwise fluid leaks from the bolt area. This doesn't seem normal. Is there an internal gasket that is bad?

A previous owner swapped in an e28 pump when the 3.5 was put in. There has been no change in steering effort in my last 6 yrs of ownership, but I've always felt it is abnormally stiff (and i've driven other vintage bmw's). When the car is jacked in the air, there doesn't seem to be any binding.

Any thoughts? Thanks!

Tim

 

[MMercury]

A previous owner swapped in an e28 pump when the 3.5 was put in. There has been no change in steering effort in my last 6 yrs of ownership, but I've always felt it is abnormally stiff (and i've driven other vintage bmw's). When the car is jacked in the air, there doesn't seem to be any binding.

Any thoughts?

I am not particularly familiar with the e28 pump, although I do recall someone else rejecting the idea of retrofitting the pump in an E3/E9 because of different hose connections. Respecting stiff steering, my first thought would be to examine, and if necessary, adjust, the steering box. It is not the most accessible adjustment, but it is doable.

Secondarily, I would double check the belt drive assembly for proper function. I would also examine the steering fluid filter (ordinarily found in the fluid reservoir) to ensure it is not restricted with debris. A plugged/contaminated filter can negatively affect the power steering function. Off hand, I am unaware of any drive pulley differences that might alter the original pump drive ratio.

As an afterthought, I recall a "stiff steering" situation occurred when experimenting with a large front sway bar of unknown origin on an E9. Although it fit both an E3, E9, it may have been originally intended for an E12/E24. From memory, the bar was >27mm. The bar clearly stiffened the front end, but it also affected steering geometry to the extent that the steering felt hampered and the wheel was slow to return to center. Disconnecting the links returned the steering operation to normal. Original bars were reinstalled.

 

[jmackro]

I recall a "stiff steering" situation occurred when experimenting with a large front sway bar of unknown origin on an E9. ... The bar clearly stiffened the front end, but it also affected steering geometry to the extent that the steering felt hampered and the wheel was slow to return to center. Disconnecting the links returned the steering operation to normal.

I'm not questioning that this happened, but I'm having trouble figuring out how a stiffer sway bar could affect front end geometry. More caster or more wheel offset will affect steering effort, but a stiffer bar wouldn't change either.

 

[MMercury]

This happened many years ago. I don't have much of an explanation other than "if" the the bar was ill-fitting, it may have over-stressed the control arms - even when the steering wheel was centered and the vehicle was traveling straight ahead where the suspension would be "resting." This likely hampered each front corner's independence and "may" have impacted camber, especially when the wheels were turned and possibly even caster. Perhaps it somehow removed slop in worn control arm bushings, strut rods and/or upper strut mounts?


Other than thickness and weight, I can't recall how the bar differed dimensionally from the original and various other aftermarket bars, but, the links were not necessarily vertical - as I contemplated some slight modification. Inverting the bar may not have been a possibility due to clearance issues, but I can't say for certain. It was obvious something was not right from the initial installation. Once the engine was running with power steering engaged, the stiffness was readily apparent at the first turn of the wheel.

I vaguely recall re-checking the toe, which hadn't changed, and drove the car on a few errands. The handling characteristics (too much oversteer) were also not to my liking, so without further thought, the bar was disconnected and ultimately relegated to a friend's garage.

I did say it was an afterthought . . . :???:

 

[Peter Coomaraswamy]

Just a thought, but the strut bearings can cause a stiff steering response. You can not tell when the wheels are hanging free but under load it can be brutal. The Polaris coupe I'm working on had horribly corroded bearings and it took allot of effort to turn the wheel. That coupe had been sitting for 11 years which explains a little but yours may be gradually degenerating and the PO may have put the strut washers in backwards. That mistake may manifest itself in a few idiosyncrasies, one of which could be stiffer steering.

May be way off but trying to help-

 

[Bav3.5]

Thanks for the answers everyone! My filter looks fine and is only 10k mi old. Interesting comments about the sway bars. I'm pretty sure I have e12 bars. I think I'll check the strut bearings next.

Any other direct experiences swapping over to a later pump as the only variable? Also, does it make sense that fluid is leaking from the mounting bolt area unless I tighten the heck out of it (basically over torquing it)? This seems bizarre that the design would allow such a leak.

 

[HB Chris]

If strut washers are in upside down wheel won't return to center after a turn by itself.